Dense Fog Advisory 13, NWS Milwaukee, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1046 PM CDT SUN APR 29 2012

.UPDATE...RAIN IS DECREASING IN COVERAGE FROM SOUTH TO NORTH AS
DRY SLOT AND AXIS OF SHORTWAVE TROUGH MOVE INTO THE REGION. DO
EXPECT AT LEAST LGT SCT SHOWERS TO CONTINUE THROUGHOUT THE NIGHT
DUE TO 925-700 MB WARM ADVECTION AND ANOTHER PASSAGE OF A WEAK
SHORTWAVE TROUGH THAT IS CURRENTLY OVER WRN IA. AT THE SFC...AN
INVERTED SFC TROUGH WILL MOVE ACROSS THE CWA BTWN 08Z AND 15Z. THE
LIGHT WINDS WITH THE TROUGH PASSAGE AND MOIST LOW LEVELS WILL LEAD
TO AREAS OF FOG.

&&

.AVIATION/06Z TAFS/...SCT SHOWERS WILL CONTINUE THROUGH THE
OVERNIGHT DUE TO WARM ADVECTION AHEAD OF AN INVERTED SFC TROUGH.
THE INVERTED SFC TROUGH WILL PASS FROM WEST TO EAST ACROSS SRN WI
FROM 08Z-15Z. THE CIGS WILL LOWER TO 400-500FT WITH VSBYS FALLING
TO 1-2 MILES. STRATUS CLOUDS WILL LINGER THROUGH MONDAY DUE TO
WEAK FLOW IN THE WAKE OF THE TROUGH PASSAGE. THE STRATUS WILL LIFT
TO MVFR CIGS BY THE MIDDLE OF THE DAY AND POSSIBLY BECOME VFR CIGS
AROUND 3.5 KFT BY LATE AFTERNOON.

&&

.PREV DISCUSSION... /ISSUED 935 PM CDT SUN APR 29 2012/

UPDATE...RAIN IS DECREASING IN COVERAGE FROM SOUTH TO NORTH AS
DRY SLOT AND AXIS OF SHORTWAVE TROUGH MOVE INTO THE REGION. DO
EXPECT AT LEAST LGT SCT SHOWERS TO CONTINUE THROUGHOUT THE NIGHT
DUE TO 925-700 MB WARM ADVECTION AND ANOTHER PASSAGE OF A WEAK
SHORTWAVE TROUGH THAT IS CURRENTLY OVER WRN IA. AT THE SFC...AN
INVERTED SFC TROUGH WILL MOVE ACROSS THE CWA BTWN 09Z AND 15Z. THE
LIGHT WINDS WITH THE TROUGH PASSAGE AND MOIST LOW LEVELS WILL LEAD
TO AREAS OF FOG.

PREV DISCUSSION... /ISSUED 334 PM CDT SUN APR 29 2012/

VERY SHORT TERM...TONIGHT AND MONDAY...FORECAST CONFIDENCE IS HIGH.

THE LARGER SYNOPTIC FEATURE LIFTING OUT OF THE CENTRAL PLAINS LOOKS
A WHOLE LOT MORE IMPRESSIVE ON SATELLITE VS THE CORRESPONDING 500MB
CHARTS EARLY THIS AFTERNOON. THIS IS CLEARLY A NICE SYNOPTIC SYSTEM
COMING AT US AND SHOULD BRING THE ENTIRE AREA SOME RAIN TONIGHT
GIVEN THE UNDERLYING. THERE IS FAIRLY DEEP AND RATHER VIGOROUS
UPWARD VERTICAL MOTION MOVING IN THIS EVENING WITH THE UPPER JET
SUGGESTING SOME COUPLING OF ENTRANCE/EXIT REGIONS OF TWO JET
SEGMENTS. THE 850MB JET AT THE SAME TIME INCREASES TO 30 TO 40
KNOTS...NOSING INTO SOUTHERN WISCONSIN AND TRIGGERING A VERY
IMPRESSIVE SURGE OF MOISTURE. MIXING RATIOS AT 800MB GO FROM 2.5G/KG
AT MID DAY SUNDAY TO 8.5G/KG AT MIDNIGHT.  THE 850MB LOW AND WARM
FRONT TRACK RIGHT THROUGH THE FORECAST AREA OVERNIGHT. THE SFC LOW
AND WARM FRONT SHOULD PASS JUST TO OUR SOUTH.  EVERY MODEL HAS OUR
ENTIRE FORECAST AREA GETTING HIT WITH 1/4 TO 1/2 INCH OF RAIN
TONIGHT. A FEW ARE FOCUSING THE HEAVIEST PRECIP FROM MADISON ON
WEST...CLOSER TO THE BEST CONVERGENCE WITH THE 850MB JET. OTHERS ARE
MORE EQUAL OPPORTUNITY FOR THE AREA. INSTABILITY IS RATHER
WEAK...BUT THE SOUNDINGS STILL SHOW SOME SKINNY REGIONS...GOOD FOR A
SLIGHT CHANCE OF THUNDER...ESPECIALLY GIVEN THE MOISTURE SURGE COMING
AT US.

THE LOW PUSHES OFF TO THE EAST MONDAY MORNING. THERE MAY STILL BE SOME
SHOWERS IN THE FAR SOUTHEAST BETWEEN 12-15Z...OTHERWISE LOOK FOR
CLOUDS IN THE MORNING WITH SOME BREAKS POSSIBLE IN THE AFTERNOON.
NOT BAD TEMP WISE AS WINDS TURN WESTERLY AND 925MB TEMPS DON/T
REALLY TANK.

SHORT TERM...MONDAY NIGHT THROUGH WEDNESDAY NIGHT.

MONDAY NIGHT...FORECAST CONFIDENCE MEDIUM TO HIGH.

VERY WEAK RIDGING BETWEEN SHORT WAVE TROUGHS MONDAY NIGHT. 12Z NAM
FASTEST WITH 700 MB WAA BUT FORECAST SOUNDINGS SHOW MOISTENING
LIMITED TO 700-600 MB LAYER...WITH WEAK 850-700MB FRONTOGENESIS...
AND VERY DRY BELOW WITH DRY FLOW AROUND RETREATING SURFACE HIGH
KEEPING BETTER LOW-LEVEL MOISTURE RETURN TO THE WEST. FOCUS OF 850MB
THERMAL/MOISTURE ADVECTION ALSO WELL WEST. WILL LEAVE DRY...BUT WITH
INCREASING MID CLOUDS IN THE SOUTHWEST. LOW TEMPERATURES WILL BE
REACHED AROUND 06Z..THEN STEADY OUT ALONG THE LAKE WHILE SLOWLY
RISING INLAND.

TUESDAY...FORECAST CONFIDENCE MEDIUM.

PERSISTENT BUT WEAK WARM AIR ADVECTION DURING THE DAY...WITH FOCUS
OF STRONGEST LOW LEVEL FLOW STAYING TO THE WEST OVER THE ERN DAKOTAS
AND MN. THERE IS A WEAK SHORT WAVE MOVING ACROSS ILLINOIS DURING THE
AFTERNOON WITH 1000-850MB THETA E ADVECTION INCREASING AHEAD OF THIS
WEAK WAVE. CAPE BUILDS CLOSE TO 800-1000 J/KG IN THE FAR WEST AND
SOUTH...THEN DROPS OFF MARKEDLY TO THE NORTH. BLENDED POPS REFLECT
THIS WELL LIMITING CHANCE POPS TO THE SOUTH. LEANED TOWARDS COOLER
SIDE OF GUIDANCE NUMBERS SINCE CLOUDS AND EXPECTED PRECIPITATING
WILL TEMPER THE WARMER 925 MB TEMPERATURES.

TUESDAY NIGHT...FORECAST CONFIDENCE MEDIUM.

FOCUS OF LOW-LEVEL JET SHIFTS TOWARD STATE...THOUGH IT WEAKENS AS
INITIAL WAVE LIFTS NORTHWARD FROM NRN MN INTO CANADA. STRONGER 850
MB WINDS WILL BE FARTHER SOUTH...TIED TO LEE CYCLOGENESIS IN THE
CENTRAL PLAINS. BETTER CHANCE FOR PRECIPITATION LOOKS TO BE BETWEEN
06Z AND 12Z WEDNESDAY BASED ON TIMING OF WEAK ISENTROPIC LIFT AND
LAYER Q-VECTOR CONVERGENCE. WILL HOLD POPS TO CHANCE CATEGORY FOR
NOW. WARM OVERNIGHT LOWS INLAND IN THE UPPER 50S TO LOW 60S WHILE
FAR EAST COOLS INTO THE MID 50S WITH SOUTHEAST WINDS BEFORE WINDS
SHIFT SOUTH AFTER MIDNIGHT.

WEDNESDAY AND WEDNESDAY NIGHT...FORECAST CONFIDENCE LOW TO MEDIUM.

HIGH CONFIDENCE OF PRECIPITATION...BUT LOW CONFIDENCE CONCERNING
TIMING AND RESULTANT SEVERE POTENTIAL. DIFFERING PLACEMENT...
STRENGTH AND TIMING OF SHORT WAVE ENERGY AMONG THE MODELS LEADS TO
DIFFERENCES IN PLACEMENT OF STRONGER LOW-LEVEL WINDS AND BEST
THERMAL ADVECTION/FORCING. A CONSENSUS BLEND FAVORS SLOWER
GFS/ECMWF...WITH LIKELY POPS FOR THE NORTHWEST CWA...MAINLY FOR THE
AFTERNOON...THEN LIKELY EVERYWHERE FOR WEDNESDAY NIGHT...FAVORING
THE EVENING. HIGH TEMPERATURES IN THE MID TO UPPER 70S EVERYWHERE ON
SOUTHWEST WINDS AND STEEP MID LEVEL LAPSE RATES HELPING TO PRODUCE
SURFACE-BASED CAPE VALUES AROUND 2000 J/KG BY WEDNESDAY
EVENING...WITH 0-6KM BULK SHEAR OF 30-35 KNOTS. LIMITING FACTORS
INCLUDE REDUCED HEATING DUE TO  CONVECTIVE DEBRIS FROM UPSTREAM
CONVECTION REDUCING INSTABILITY. WILL KEEP MENTION OF SEVERE IN THE
HWO. ALL SOLUTIONS KEEP SURFACE TROUGH NORTHWEST OF CWA THROUGH 12Z
THURSDAY...SO OVERNIGHT LOWS IN THE 60S EVERYWHERE.

LONG TERM....LONG TERM...THURSDAY THROUGH SUNDAY. FORECAST CONFIDENCE LOW.

IN SPITE OF MODEL DIFFERENCES...THEY GENERALLY AGREE IN KEEPING
SOUTHERN WISCONSIN CLOSE TO...OR JUST ON THE WARM SIDE OF THE 850 MB
BAROCLINIC ZONE RUNNING PARALLEL TO WEST-SOUTHWEST UPPER FLOW INTO
FRIDAY. CHANCES OF SHOWERS AND/OR THUNDERSTORMS AS WEAK WAVES MOVE
THROUGH THE FLOW...BUT LITTLE AGREEMENT TO TIMING. BLENDED SOLUTION
BRINGS HIGHS IN THE 70S THURSDAY AND FRIDAY...THOUGH COOLER IN THE
FAR EAST FRIDAY AS LIGHT GRADIENT WINDS TURN NORTHEAST TO EAST IN
THE AFTERNOON. GFS AND ECMWF TO AGREE THAT COOLER AIR WILL SETTLE
INTO SOUTHERN WISCONSIN BY SUNDAY...BUT ONLY TO SEASONAL
NORMS...WITH ANOTHER WAVE APPROACHING FROM THE ROCKIES THAT WILL
DETERMINE OUR EARLY WEEK WEATHER NEXT WEEK.

AVIATION/00Z TAFS/...

LOOK FOR GRADUALLY DETERIORATING CONDITIONS THROUGH THE OVERNIGHT
HOURS...CULMINATING IN IFR CIGS DEVELOPING BETWEEN 09-12Z TONIGHT.
THE EVENING STARTS OUT WITH MID LEVEL CLOUDS...BUT WILL LOWER
QUICKLY AS RAIN PUSHES IN WITH THE APPROACH OF A LOW PRESSURE SYSTEM
LIFTING OUT OF THE CENTRAL PLAINS.  RAIN SHOULD HIT KMSN BY 00-01Z
AND THE SOUTHEAST TAF SITES ABOUT 02-03Z.  RAIN SHOULD CONTINUE IN A
PRETTY STEADY FASHION THROUGH ABOUT 10-11Z WHEN IT TAPERS TO SOME
SHOWERS BEFORE ENDING ENTIRELY BY OR SHORTLY AFTER 12Z.  LOOK FOR
THE IFR CIGS TO RISE TO MVFR DURING MONDAY MORNING AND VFR MONDAY
AFTERNOON.  WINDS WILL BE EASTERLY THROUGH MIDNIGHT...THEN LOOK FOR
A WIND SHIFT TO THE WEST BEFORE SUNRISE AS A TROF PASSES THROUGH.

MARINE...

EAK LOW PRESSURE PASSING TO THE SOUTH OF LAKE MI TONIGHT AND MONDAY
WILL RESULT IN A TIGHTENING PRESSURE GRADIENT.  SURFACE WINDS ARE
EXPECTED TO REMAIN ONSHORE RESULTING IN LOW LEVEL INVERSION.  LATEST
MODIS IMAGERY AND MID LAKE BUOY CONTINUE TO SHOW SRN LAKE MI SFC
TEMPS IN THE LOW TO MID 40S.  EXPECT INVERSION TO PREVENT STRONGER
WINDS FROM REACHING LAKE SURFACE TNGT.  HOWEVER...WIND GUSTS
EXCEEDING 20KTS MAY BE FELT AT SGNW3 AND KNSW3 WHERE ANEMOMETER
HEIGHTS ARE 60FT ABV LAKE SFC.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

UPDATE...GEHRING
TONIGHT/MONDAY AND AVIATION/MARINE...DAVIS
MONDAY NIGHT THROUGH SUNDAY...REM

HAZARDOUS WEATHER OUTLOOK...UPDATE
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
732 PM CDT SUN APR 29 2012

WIZ046-047-051-052-056>060-062>072-302100-
MARQUETTE-GREEN LAKE-FOND DU LAC-SHEBOYGAN-SAUK-COLUMBIA-DODGE-
WASHINGTON-OZAUKEE-IOWA-DANE-JEFFERSON-WAUKESHA-MILWAUKEE-
LAFAYETTE-GREEN-ROCK-WALWORTH-RACINE-KENOSHA-
732 PM CDT SUN APR 29 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
WISCONSIN...SOUTH CENTRAL WISCONSIN AND SOUTHEAST WISCONSIN.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SUNDAY

SEVERAL ROUNDS OF THUNDERSTORMS ARE EXPECTED FROM TUESDAY NIGHT
INTO FRIDAY AS WARMER...MORE HUMID AIR SETTLES OVER SOUTHERN
WISCONSIN. SEVERAL LOW PRESSURE SYSTEMS MOVING NORTHEAST ALONG A
BOUNDARY THAT WILL BE DRAPED ACROSS WISCONSIN INTO THE CENTRAL
PLAINS WILL BE RESPONSIBLE FOR THE THUNDERSTORMS.

THERE IS A POTENTIAL FOR SEVERE THUNDERSTORMS TUESDAY NIGHT AND
WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED LATER THIS WEEK.

LMZ643>646-302100-
SHEBOYGAN TO PORT WASHINGTON WI-
PORT WASHINGTON TO NORTH POINT LIGHT WI-
NORTH POINT LIGHT TO WIND POINT WI-
WIND POINT WI TO WINTHROP HARBOR IL-
732 PM CDT SUN APR 29 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF LAKE MICHIGAN.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SUNDAY

SEVERAL ROUNDS OF THUNDERSTORMS ARE EXPECTED FROM TUESDAY NIGHT
INTO FRIDAY AS WARMER...MORE HUMID AIR SETTLES OVER THE WESTERN
GREAT LAKES. SEVERAL LOW PRESSURE SYSTEMS MOVING NORTHEAST ALONG
A BOUNDARY THAT WILL BE DRAPED ACROSS WISCONSIN INTO THE CENTRAL
PLAINS WILL BE RESPONSIBLE FOR THE THUNDERSTORMS.

THERE IS A POTENTIAL FOR SEVERE THUNDERSTORMS TUESDAY NIGHT AND
WEDNESDAY.

GEHRING
WWW.WEATHER.GOV/MKX